Method and Apparatus for Forming Contoured Composite Laminates

ABSTRACT

A composite laminate such as a hat-type stringer is formed on a contoured mandrel using a combination of mechanical sweeping and vacuum forming.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of prior co-pending U.S.patent application Ser. No. 14/279,725 filed May 16, 2014, the entiredisclosure of which is incorporated by reference herein.

BACKGROUND INFORMATION

1. Field

The present disclosure generally relates to the fabrication of compositestructures, and deals more particularly with a method and apparatus forfabricating concave and convex stiffeners such as stringers, especiallythose that are contoured.

2. Background

Composite laminate structural stiffeners are sometimes required to havecomplex contours tailored to particular applications. For example, inthe aircraft industry, composite laminate stringers used to stiffenaircraft skins are sometimes contoured in one or more planes in order tomatch changes in the geometry of the skins.

Layup and forming of structural stiffeners with complex contours can bechallenging because of the tendency of the uncured composite prepregmaterial to bridge or wrinkle in the areas of contours. Dry fabric clothused to make fiber performs that are subsequently infused with resin mayalso wrinkle when formed to a desired preform shape having contours,particularly when tackified and/or multiple plies of the cloth are beingformed to shape simultaneously. Bridging results in undesired resinrich-areas in the laminate, while wrinkling may produce undesiredlocalized high stress concentrations. In order to minimize theseproblems, composite laminate structural stiffeners such as stringers areusually laid up by hand in order to minimize bridging and wrinkling.However, even using hand layup techniques, bridging and wrinkling of thelaminate sometimes occurs which requires hand rework of the stiffener,typically using patches. Hand layup of stiffeners and rework ofstiffener non-conformities is both labor-intensive and time-consuming,and therefore expensive.

Accordingly, there is a need for a method and apparatus for laying upand forming contoured composite stiffeners such as composite laminateprepreg stringers, that reduce non-conformities and touch labor. Thereis also a need for a method and apparatus of the type mentioned abovewhich may increase production throughput while reducing factory floorspace required for stiffener production.

SUMMARY

The disclosed embodiments provide a method and apparatus for partiallyautomating the fabrication of composite prepreg laminate stiffeners suchas stringers, which reduces nonconformities and attendant rework, whilereducing touch labor and increasing factory throughput. The disclosedmethod and apparatus employ a combination of mechanical sweeping andvacuum forming to form composite prepreg plies onto complex contours ofa tool without substantial bridging or wrinkling.

According to one disclosed embodiment, apparatus is provided for formingplies of material onto a mandrel having contours. The apparatus includesa ply sweeper for sweeping the plies onto the contours of the mandrel,and a presser independently displaceable relative to the ply sweeper forpressing a portion of the plies against the mandrel. The apparatusfurther includes at least one powered actuator coupled with presser fordisplacing the presser relative to the ply sweeper.

According to another disclosed embodiment, apparatus is provided forforming composite plies on a mandrel contoured along its length andhaving a cap, a pair of webs, and a pair of flanges configured to form ahat-shaped stringer. The apparatus includes a frame, a ply sweeper, apresser and at least one linear actuator. The ply sweeper is mounted onthe frame and is configured to sweep the composite plies down onto andover the webs of the mandrel. The presser is mounted on the frame and isextensible relative to the ply sweeper. The presser is configured topress a portion of the composite plies against the mandrel. The linearactuator is mounted on the frame and is coupled with presser forextending the presser relative to the ply sweeper.

According to still another disclosed embodiment, a method is provided offorming a composite stiffener contoured along its length. The methodincludes placing at least one composite ply over a mandrel andpositioning a ply sweeper and a presser above the mandrel. The methodalso includes extending the presser relative to the ply sweeper using alinear actuator. The method further includes clamping a portion of thecomposite ply against the mandrel, including moving the presser and plysweeper toward the mandrel until the presser forces a portion of thecomposite ply against the mandrel. The method also includes sweeping thecomposite ply down over the mandrel while the portion of the compositeply is clamped against the mandrel.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description of an illustrative embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a perspective view of a composite prepreglaminate stringer having complex contours.

FIG. 2 is an illustration of a sectional view taken along the line 2-2in FIG. 1 showing roll in the stringer, wherein the X-Y plane isindicated by a broken line.

FIG. 3 is an illustration of a sectional view taken along line 3-3 inFIG. 1, showing another roll in the stringer, wherein the X-Y plane isindicated by a broken line.

FIG. 4 is an illustration of a top plan view of the stringer shown inFIG. 1, showing changes in yaw.

FIG. 5 is an illustration of a side elevational view of the stringershown in FIG. 1, showing changes in pitch.

FIGS. 6-12 are illustrations of cross-sectional views of apparatus formechanical sweeping and vacuum forming composite prepreg plies on amandrel having complex contours, respectively showing sequential formingsteps.

FIG. 13 is an illustration of a side elevational view of a ply sweeperalong with a vacuum bagged composite laminate ply.

FIG. 14 is an illustration of an isometric, cross sectional view takenalong the line 14-14 in FIG. 13.

FIGS. 15-18 are illustrations of cross-sectional views of an alternateembodiment of apparatus for mechanical sweeping and vacuum formingcomposite plies on a contoured mandrel.

FIG. 19 is an illustration of a side elevational view of an alternateembodiment of a ply sweeper, portions of the ply sweeper having beenbroken away to reveal a spreader plate.

FIGS. 20 and 21 are illustrations of cross-sectional views showing theply sweeper of FIG. 19 sweeping a ply over a contoured mandrel.

FIGS. 22-24 are illustrations of cross-sectional views showing analternate embodiment of the ply sweeper progressively forming a ply overa contoured mandrel.

FIG. 25 is an illustration of a cross-sectional view showing anotherembodiment of the ply sweeper.

FIG. 26 is an illustration of a cross-sectional view showing a furtherembodiment of the ply sweeper in which the cap is pressed and fingersare held apart prior to sweeping.

FIG. 27 is an illustration of a cross-sectional view showing stillanother embodiment of the ply sweeper in which the sides of the cappresser are pulled toward one another as contact is made with the cap.

FIGS. 28 and 29 are illustrations of cross-sectional views showing afurther embodiment of the ply sweeper progressively forming a ply over acontoured mandrel in which the finger halves are split.

FIG. 30 is an illustration of a cross-sectional view showing a furtherfeature of the split finger ply sweeper in which the finger halvesrotate to sweep the cap and cap/web outside radius prior to fullengagement of the web/flange inside radius.

FIG. 31 is an illustration of a cross-sectional view showing analternate embodiment of the apparatus for mechanically sweeping andvacuum forming plies on a contoured mandrel.

FIG. 32 is an illustration of an end elevational view of one embodimentof a forming unit for forming composite laminate prepreg plies on amandrel contoured in one plane.

FIG. 33 is an illustration of an end elevational view of anotherembodiment of a forming unit for forming composite laminate prepregplies on a mandrel contoured in multiple planes.

FIG. 34 is an illustration of a combined block and diagrammatic view offorming apparatus employing the forming units of the FIG. 33 arrangedside-by-side.

FIG. 35 is an illustration of an end elevational view of a mobile cartinterfacing with a forming station.

FIG. 36 is an illustration of a combined block and diagrammatic view offorming apparatus employing the mobile cart and forming station shown inFIG. 35.

FIG. 37 is an illustration of a perspective view of an alternate form ofa forming apparatus.

FIG. 38 is an illustration of a side elevational view of one of theformer modules shown in FIG. 37.

FIG. 39 is an illustration of a front perspective view of the formingapparatus shown in FIG. 37.

FIG. 40 is an illustration of an isometric view of a portion of theforming apparatus shown in FIGS. 37 and 39.

FIG. 41 is an illustration of a flow diagram of a method of formingcontoured composite prepreg plies.

FIG. 42 is an illustration of a flow diagram of a method of formingcontoured composite prepreg stringers.

FIG. 43 is an illustration of a flow diagram of a method of laying upand forming composite prepreg laminate stiffeners.

FIG. 44 is an illustration of a side view of an alternate embodiment ofthe forming head.

FIG. 45 is an illustration of the area designated as “FIG. 45” in FIG.44.

FIG. 46 is an illustration of an end view of the forming head shown inFIG. 44.

FIG. 47 is an illustration of a perspective view of a portion of theforming head of FIG. 44, showing the presser engaging the cap section ofa fully formed and compacted stiffener.

FIG. 48 is an illustration of a perspective view of a presser section.

FIG. 49 is an illustration of an elevational view of one and of thepresser section of FIG. 48.

FIG. 50 is an illustration of an elevational view of the other end ofthe presser section of FIG. 48.

FIG. 51 is an illustration of a side elevational view showing a jointbetween two of the presser sections.

FIG. 52 is an illustration of a top plan view of the joint between thepresser sections shown in FIG. 51.

FIG. 53 is an illustration of an end view of the forming head, alignedabove a mandrel in preparation for carrying out forming operation.

FIG. 54 is an illustration similar to FIG. 53 but showing forming headhaving descended toward the mandrel, causing the presser to clamp aportion of a ply on the Of the mandrel.

FIG. 55 is an illustration of the area designated as “FIG. 55” in FIG.54.

FIGS. 56-58 are illustrations similar to FIG. 53, showing sequentialforming of the plies.

FIG. 59 is an illustration of a combined block and diagrammatic view ofa system for controlling multiple forming heads used to form a contouredcomposite stiffener.

FIG. 60 is an illustration of a flow diagram of a method of forming acomposite stiffener contoured along its length.

FIG. 61 is an illustration of a flow diagram of aircraft production andservice methodology.

FIG. 62 is an illustration of a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring to FIGS. 1-5, the disclosed embodiments relate to a method andapparatus for laying up, forming and handling a composite prepregstructure such as a multi-ply laminate stiffener. The stiffener may be,for example, a contoured composite stringer 50. The stringer 50,sometimes referred to as a hat stringer 50 includes a cap 56, a pair ofwebs 58, and a pair of flanges 54. An inside radius 60 joins the web andflange surfaces. While a hat type stringer 50 is illustrated, a widevariety of other cross-sectional stiffener shapes may be formed by thedisclosed method and apparatus discussed below. The stringer 50 isformed from laminated plies of a fiber reinforced polymer resin such as,without limitation, carbon fiber epoxy. In one example, the stringer 50may be fabricated using plies of unidirectional prepreg that are laid upand formed individually, or in groups (i.e., multiple plies).

The stringer 50 may have one or more complex contours along its length.Any of these contours may be constant or varying. For example, theillustrated stringer 50 has curvatures (see FIGS. 1 and 4) in the X-Yplane, and curvatures (FIG. 5) in the X-Z plane. Portions of thestringer 50 may also be twisted at a constant or varying angle θ (FIGS.2 and 3) in the Y-Z plane. For ease of description hereinafter,curvature in the Y-Z plane will be referred to roll (twist), curvaturein the X-Z plane will be referred to as pitch, and curvature in the X-Yplane will be referred to as yaw.

Referring now to FIG. 6, at least one flat ply 82 of material may belaid up and formed on a layup tool such as an elongate mandrel 74mounted on a tool base 84. The mandrel 74 is contoured along its lengthas well as contoured transversely. In one example, the ply of material,sometimes referred to herein as a composite or prepreg ply 82, maycomprise a unidirectional or bi-directional fiber reinforcementimpregnated with and held in a suitable resin matrix such as a thermosetor a thermoplastic. In another example, the ply 82 may be a dry fiber ora tackified fiber reinforcement which is infused with a resin after theply has been formed to the desired preform shape. The mandrel 74 has anouter contoured surface comprising a first portion and a second portion.The first portion of the contoured mandrel surface comprises a capsection 76, a pair of web sections 78, and inside radii 90. A secondportion of the contoured mandrel surface comprises a pair of flangesections 80. The cap section 76, web sections 78, inside radii andflange sections 80 all have substantially the same size, shape andlocation as the IML (inner mold line) of the stringer 50 shown in FIGS.1-5.

As will be discussed below in more detail, at least one ply 82 is laidup and formed on the mandrel 74 using a two-step process comprisingmechanical sweeping and vacuum forming. The mechanical sweeping of theply is performed by a forming head 64 which is stroked down over the websections 78, and the vacuum forming is performed by a vacuum membranesuch as, without limitation, a flexible diaphragm 86. As will becomeapparent later in the description, any of a variety of mechanisms andtechniques may be employed to perform the mechanical sweeping and thevacuum forming. As previously noted, in some embodiments, multiple plies82 may be simultaneously laid up and formed on the mandrel 74.

The forming head 64 includes a ply sweeper 65 which may comprise aplurality of longitudinally spaced mechanical forming fingers 66 thatare arranged in opposing sets thereof. In one embodiment, the formingfingers 66 may be formed of a flexible, resilient material such asplastic, composite, metal etc. The ply sweeper 65 is mounted by suitablehardware 68 to a ram which may comprise, for example and withoutlimitation, a pneumatic piston rod 70. The piston rod 70 drives the plysweeper 65 downwardly 72, causing the forming fingers 66 to initiallyclamp the ply 82 on the cap section 76 in order to maintain alignment ofthe ply 82 relative the mandrel 74 during the subsequent formingprocess. Continued downward movement of the piston rod 70 causes theforming fingers 66 to deflect outwardly while maintaining pressureagainst the ply 82, thereby sweeping the ply 82 down over, andconforming to the web sections 78 of the mandrel 74.

The flexible diaphragm 86 is disposed between the mandrel 74 and theforming head 64. The diaphragm 86 is sealed around its periphery to thetool base 84 by seals 88, forming a substantially vacuum tight chamberaround the flange sections 80. The diaphragm 86 may be formed of asuitable material such as reinforced latex, silicone or the like which,while flexible, is substantially stretchable only in one direction (inthe direction of the X-axis). In some embodiments, the diaphragm 86 maybe a separate element that is manually placed between the forming head64 and the mandrel 74. Alternatively, the diaphragm 86 along with one ormore plies 82 adhered to it may be shuttled together between the forminghead 64 and the mandrel 74. In other embodiments, however, the diaphragm86 may be attached to, and form a part of the forming head 64. In stillother embodiments discussed later herein, the diaphragm 86 may comprisean encapsulating membrane, such as tube-type flexible vacuum bag thatsurrounds the ply layup.

The sequential steps of forming the ply 82 are illustrated in FIGS.7-12, according to one method embodiment. Initially, as shown in FIG. 7,with the tips 75 of the fingers 66 spread apart sufficiently to clearthe cap section 76, the forming head 64 is displaced downwardly 72,causing the fingers 66 to initially clamp a portion of the diaphragm 86and ply 82 against the cap section 76 of the mandrel 74. With the ply 82clamped against the cap section 76, and therefore immobilized, theforming head 64 continues its downward displacement 72, causing thefingertips 75 to apply pressure to and form the ply 82 down against theweb sections 78 of the mandrel 74, as shown in FIG. 8.

Continued downward movement 72 of the forming head 64, shown in FIGS. 9and 10, causes the ply sweeper 65 to form the ply 82 against theremaining portions of the web sections 78 until the fingertips 75 reachthe inside radii 90 (FIG. 10). At this point, both the cap 56 and thewebs 58 of the stringer 50 fully match the geometry of the web sections78 of the forming mandrel 74. Next, shown in FIG. 11, with thefingertips holding the ply 82 against the mandrel 74 at the inside radii90, the diaphragm 86 is sealed to the tool base 84, and then evacuatedusing a vacuum source 94 to draw air through openings 92 in the toolbase 84.

Referring to FIG. 12, the evacuation of the diaphragm 86 causes thediaphragm 86 to draw the ply 82 down against the flange sections 80 ofthe mandrel 74, thereby completing matching the geometry of the flangesections 80 of the forming mandrel 74. With the shape of the stringer 50having been fully formed, the forming head 64 is raised, and thediaphragm 86 is drawn away, permitting removal of the fully formedstringer 50 from the mandrel 74. In some embodiments, as will bediscussed below in more detail, the mandrel 74 may also be employed totransport and place the completed stringer 50 onto a cure tool (notshown) for curing.

FIGS. 13 and 14 illustrate an embodiment of the ply sweeper 65comprising a tube 96 having a plurality of longitudinally spaced slots98 therein which define two sets of opposing, flexible forming fingers100. The tube 96 may be formed of a flexible, resilient material suchas, without limitation, plastic, and the slots 98 may be formed usingany suitable fabrication process such as sawing or cutting. The opposedflexible fingers 100 have fingertips 102 that are spaced apartsufficiently to clear the cap section 76, as best seen in FIG. 14. Inthe embodiment illustrated in FIGS. 13 and 14, a tube-type vacuum bag105 (shown in FIG. 13 only) is sleeved over the plies 82 and the mandrel74.

When evacuated, the tube-type vacuum bag 105 vacuum forms the plies 82down onto the flange sections (FIG. 12) of the mandrel 74. In someembodiments, compliance of the tube 96 to the shape of the mandrel 74may be achieved by dividing the tube 96 into a plurality of individualsections, each adjustable to match local contours of the mandrel 74. Inother embodiments, however, a single tube 96 extending along the entirelength of the mandrel 74 may be employed to perform the sweeping action.Where a single tube 96 is used, the necessary compliance of the tube 96to changing mandrel contours (roll, pitch and yaw) may be obtained byproviding the top 97 of the tube 96 with flexibility, either bysegmenting the top 97 of the tube 96, or by forming the top 97 of thetube 96 from a flexible material such as a rubber.

Depending upon the type of ply sweeper 65 being employed, it may benecessary to spread the fingertips 102 a distance that is greater thanthe width of the cap section 76 of the mandrel 74. One device forspreading or opening the fingertips 102 is shown in FIGS. 15-18.Referring to FIG. 15, an inflatable bladder 104 is disposed inside thetube 96, as shown in FIGS. 13 and 14. The bladder 104 may be inflatedusing any suitable pressurized fluid, such as air. With the bladder 104fully inflated, as shown in FIG. 15, a lower portion 104 a of thebladder 104 extends below the fingertips 102.

Referring to FIG. 16, as the forming head 64 is displaced downwardly,the lower portion 104 a of the bladder 104 initially contacts the ply82, clamping it against the cap section 76 of the mandrel 74 in order tomaintain alignment of the ply 82 relative to the mandrel during thesubsequent forming process. When the fingertips 102 clear the capsection 76 and began forming the ply 82 against the web sections 78, thebladder 104 is deflated, as shown in FIG. 17, permitting the fingerforming process to continue. The bladder 104 remains substantiallydeflated until the fingertips 102 have formed the ply 82 down into theinside radii 90, as shown in FIG. 18.

Other techniques may be employed, where necessary, to spread thefingertips 102 a distance that is sufficient to clear the cap section 76of the mandrel 74. For example, referring to FIG. 19, a longitudinallyextending spreader plate 110 may be installed inside the tube 96 andused to open the fingers 100. The spreader plate 110 has threaded studs106 that pass through the top of the tube 96. Wingnuts 108 or similarfasteners on the threaded studs 106 may be adjusted to alter thevertical position of the spreader plate 110. In some embodiments, apower operated device such as a pneumatically or electrically drivenscrew drive (not shown) may be employed in lieu of the wing nuts 108 toprovide automated adjustment of the position of the spreader plate 110.Referring to FIG. 20, as the spreader plate 110 is drawn upwardly inresponse to adjustment of the wingnuts 108, the spreader plate 110engages the inner diameter of the tube 96, forcing the opposing sets offingertips 102 to spread 114 until they clear the cap section 76 themandrel 74. Continued downward movement of the tube 96 (see FIG. 21)allows the fingertips 102 to complete forming of the web sections 58 ofthe stringer 50.

FIGS. 22-24 illustrate another embodiment of the sweeper 65 havingforming fingers 100 similar to those previously described. In thisembodiment, movable forming elements 116 are captured between thefingertips 102 and the ply 82. The forming elements 116 have flatsurface areas 116 a that engage a greater surface area of the ply 82,compared to the embodiments shown in FIGS. 19-21 in which only the outerends of the fingertips 102 engage the ply 82. As the tube 96 isdisplaced downwardly, as shown in FIG. 23, the forming elements 116pivot relative to the fingertips 102, forcing the ply down against theweb sections 78 of the mandrel 74. The forming elements 116 continuepivoting until they form the ply 82 down into the inside radii 90, asshown in FIG. 24.

A variety of other techniques may be employed to clamp the ply 82 to thecap section 76 in order to maintain alignment of the ply 82 relative tothe forming mandrel 74 as the ply 82 is being formed. For example,referring to FIG. 25, a clamping element 120 is mounted on the end of arod 118 that passes through the top of the tube 96. Downwarddisplacement of the rod 118 brings a clamping element 120 into contactwith the ply 82, forcing the ply 82 against the cap section 76. With theply 82 clamped against the cap section 76, the tube 96 is displaceddownwardly relative to the rod 118, allowing the forming fingers 100 tosweep the ply 82 over the web sections 78.

FIG. 26 illustrates another embodiment of the forming head 64 in whichclamping of the ply 82 to the cap section 76 is performed by aspring-loaded clamping member 124 having a clamping surface 128 that isapproximately the same width as the cap section 76. The clamping member124 may comprise, for example and without limitation, rigid plastichaving a hollow core. The use of a relatively broad clamping surface 128may assist in maintaining the cap 56 relatively flat during the formingprocess. The clamping member 124 is attached to a rod 122 surrounded bya compression spring 126 that is trapped between the clamping member 124and the inside surface of the tube 96. As the forming head 64 movesdownwardly, the clamping member 124 makes initial contact with the ply82.

Continued downward movement of the forming head compresses the spring126, which in turn loads the clamping member 124 against the ply 82 andthe cap section 76. As the tube 96 continues its downward movement, thefingers 100 sweep the ply 82 over the web sections 78, and the rod 122is allowed to move up through the top of the tube 96. In someembodiments, as shown in FIG. 27, it may be necessary or desirable toplace a membrane over the bottom of the clamping member 124 to assist inflexing the sides of the clamping member 124 toward the webs as the capis clamped, further providing a smooth transition of the fingers fromthe sides of the clamping member 124 to the webs 78.

Attention is now directed to FIGS. 28 and 29 which illustrate anotherembodiment of the forming head 64 which utilizes a cam mechanism 132 forcontrolling the position of the forming fingers 100 during the plysweeping process. The cam mechanism 132 comprises a cam member 138wedged between a pair of a pair of spreader blocks 134, 136 which act ascam followers that are displaced by downward movement of the cam member138. The spreader blocks 134, 136 are respectively attached to two setsof independent and opposing forming fingers 100. The spreader blocks134, 136 are spring-loaded 135 toward each other, causing fingers 100 tonormally spread apart. However, pressure applied to the spreader blocks134, 136 by the cam member 138 overcomes the force of thespring-loading, forcing the fingers 100 toward each other.

FIG. 28 shows the fingertips 102 spread apart a distance that issufficient to clear the cap section of the mandrels 74. Downwardmovement the cam member 138 (see FIG. 29) causes the fingertips 102 tomove toward each other and sweep ply 82 onto the web sections 78 as theforming head 64 moves downwardly. While a cam mechanism has beendisclosed, a variety of other known mechanism may be employed to controlthe position of the forming fingers 100 during the ply sweeping process.

Attention is now directed to FIG. 30 which illustrates anotherembodiment of the forming head 64 which employs a link mechanism 137 forcontrolling the movement of fingers 100 during a ply sweeping operation.A drive link 131 is pivotally connected to one end of each of twoconnecting links 139, 141. The other ends of the connecting links 139,141 are respectively pivotally connected to a pair of spreader blocks134, 136 that are fixed to two separate, opposed sets of the formingfingers 100. A downward force F applied to the drive link 131 istransmitted through the connecting links 139, 141 to the fingers 100.The fingers 100 rotate 143 in response to the force applied by theconnecting links 139, 141, thereby controlling the movement of thefingertips 102 during sweeping of a ply 82 down over the web sections 78of the mandrel 74. A pair of blocks 145 act as stops that engage thespreader blocks 134, 136 to limit the rotation of the fingers 100.

FIG. 31 illustrates an alternate embodiment of a forming apparatus, inwhich the force used to displace the sweeper 65 is supplied by an outerdiaphragm or vacuum bag 142. In this embodiment, the mandrel 74 ismounted on a tool base 140, along with a pair of sealing blocks 148.Each of the sealing blocks 148 extends longitudinally along the outeredges of the flange sections 80 and includes inner and outer sealsurfaces 150, 152. An inner diaphragm 86 (discussed previously) isplaced over a ply 82 and is adapted to be sealed against the inner sealsurface 150. The outer diaphragm 142 covers the forming head 64 and issealed to the outer seal surface 152 of blocks 148, forming a vacuumtight outer chamber 167. A caul plate 144 may be placed between the plysweeper 65 and the outer diaphragm 142 in order to concentrate anddirect pressure P from the outer diaphragm 142 onto the ply sweeper 65.A pair of vacuum lines 162, 164 pass through the mandrel 74 and areadapted to evacuate the area beneath the inner diaphragm 86. A thirdvacuum line 170 is coupled through a valve 168 to both the ambientatmospheric air 166 and the vacuum regulator 156. The vacuum line 170passes through one of the blocks 148 and communicates with outer chamber167 beneath the outer diaphragm 142.

In operation, a ply 82 is placed over the mandrel 74, and the innerdiaphragm 86 is placed over ply 82 and sealed to the inner seal surfaces150. The outer diaphragm 142 along with the forming head 64 is thenpositioned over the mandrel 74, and the outer diaphragm 142 is sealed tothe outer seal surfaces 152. A partial vacuum is then drawn on both theinner and outer diaphragms 86, 142 respectively, using vacuum lines 164,170. The partial vacuum in the outer chamber 167 produces a pressure Pthat forces the forming head 64 downwardly, causing the fingertips 102of the ply sweeper 65 to form the ply 82 down over the web sections 78of the mandrel 74.

When the fingertips 102 bottom out at the inside radii 90, a hard vacuumis pulled on the inner diaphragm 86 while the partial vacuum on theouter diaphragm 142 is released through vacuum line 170 and valve 168.The hard vacuum pulled on the inner diaphragm 86 forms the ply 82 downonto the flange sections 80 of the mandrel 74. In order to assist inremoving the sealed inner diaphragm 86, positive pressure may be appliedto the inner diaphragm 86 using the line 162. The inner and outerdiaphragms 86, 142, along with the forming head 64 are then removed toallow the fully formed ply 82 to be removed from the mandrel 74.

It should be noted here that, as previously mentioned, other techniquesand mechanisms can be employed to actuate a stroke of the forming head64 such as, without limitation, clamps, pneumatic cylinders, threadedscrew drives, robots, hoses and outer diaphragms, to name only a few.

Attention is now directed to FIG. 32 which illustrates a portableforming unit 172 that may be used to form a portion of the length of acontoured composite laminate stringer 50. As will be discussed below inmore detail, a plurality of the forming units 172 may be assembledside-by-side to form various portions of the stringer 50 whichrespectively may have differing contours. In the example illustrated inFIG. 32, one or more composite laminate plies (not shown in FIG. 32) areformed on a mandrel 74 having one or more contours in the X-Z plane inorder to form a composite laminate stringer 50 having variations inpitch. In other embodiments, the mandrels 74 may have one or morecontours in the X-Y plane (variations in yaw), and/or one or morecontours in the Y-Z plane (variations in roll).

The portable forming unit 172 broadly comprises a former module 174mounted on a movable platform, which in one embodiment, may comprise amobile cart 188. Other forms of movable platforms are possible,depending on the application. The former module 174 includes a C-shapedframe 175 having a vertical support 176, an upper arm 178, and a lowerarm 180. The former module 174 also includes a forming head 64 mountedon a piston rod 184 of a cylinder 182 for movement along the Z-axis. Thecylinder 182 may be, for example and without limitation part of ahydraulic or pneumatic powered cylinder. The mandrel 74 is removablymounted on the lower arm 180 by any suitable means, such as a handoperated clamp (not shown).

The mobile cart 188 comprises an upright member 190 on which thevertical support 176 is mounted, as well as a cart base 192 havingwheels 194 that allow the cart 188 to be moved over a supporting surfacesuch as a factory floor (not shown). An adjustment mechanism 165 isprovided for adjusting the position and orientation of the former module174 on the upright 190 for movement along the Z axis. In one embodiment,the adjustment mechanism 165 may comprise a screw drive 196 that may bemanually or power driven to adjust the orientation of the former module174 to match the contour of local sections of the mandrel 74.

FIG. 33 illustrates an alternate embodiment of a forming unit 172 thatincludes independent adjustment of the roll, pitch and yaw of a forminghead 64, thereby allowing a composite laminate stringer 50 to be formedthat has complex contours, such as the stringer shown in FIGS. 1-5. Theforming unit 172 shown in FIG. 33 is similar to that shown in FIG. 32,but additionally has adjustment mechanisms 165 for adjusting the pitch(X-Z plane), roll (Y-Z plane) and yaw (X-Y plane) of the forming head64. The adjustment mechanism 165 includes screw drives 198, 206 and 208.Roll of the entire former module 174 may be adjusted using screw drive206, 208 to adjust the position of slides 202, 204 that support theC-shaped frame 175 on a cart upright 190. The yaw of the former module174 may be adjusted using screw drive 198 to rotate the C-shaped frame175 on the cart upright 190. It should be noted here that variousalternate mechanisms may be used to adjust the yaw, pitch and/or roll ofthe forming head 64 relative to the mandrel 74, and any or all of thesemechanisms may be part of the forming head 64, or part of the formermodule 174 or part of the cart 188. The adjustment mechanisms describedabove provide a form of passive compliance that permits the sweeper 65to be aligned with local contours of the mandrel 74.

A plurality of the forming units 172 of the type shown in FIGS. 32 and33 may be assembled together to collectively form an apparatus forforming a composite prepreg laminate having complex contours. Forexample, referring to FIG. 34, a forming apparatus 195 comprises aplurality of the forming units 172 arranged side-by-side which may bemechanically connected together by suitable mechanical interlocks 185.Each of the forming units 172 is aligned with local contours of theforming mandrel 74 and is operative to form a section of the prepreglaminate. Each of the forming units 172 comprises a former module 174that is associated with a section of the mandrel 74 and is mounted on amobile cart 188, or similar mobile platform. Each of the former modules174 includes the previously discussed features necessary to permitadjustment of yaw, pitch and roll of the forming head 64 tosubstantially match the local contouring of the mandrel 74. The numberof the forming units 172 assembled together will depend upon the lengthof the particular layup mandrel 74 being employed. The use of theindividual forming units 172 permits the forming units 172 to be readilyinterchanged, for repair or service, and provides the flexibility to addor remove forming units 172, as required to suit the particularapplication.

Attention is now directed to FIGS. 35 and 36 which illustrate apparatus205 useful in layup, forming, handling and installation of compositeprepreg laminates such as stringers. The apparatus 205 broadly comprisesone or more forming stations 226, and one or more interfacing mobilecarts 214. Each of the forming stations 226 includes a former module 240provided with a forming head 64 and a mechanism 165 for adjusting theroll, pitch and/or yaw of the forming head 64 to match local contours ofa mandrel 74, similar to the embodiments previously described. Theformer module 240 is mounted on a frame assembly 235 comprising uprights234 and a series of cross members 228, 230, 232. The frame assembly 235may be provided with wheels 194 to facilitate portability of the formingstation 226.

Each of the mobile carts 214 comprises a mandrel support table 216 onwhich at least a portion of a mandrel 74 may be supported. The spacingbetween adjacent ones of the support tables 216 substantially matchesthe spacing between adjacent ones of the former modules 240, such thateach of the support tables 216 is aligned with one of the former modules240. The support table 216 is mounted on one or more uprights 190. Theuprights 190 are attached to vertical frame members 220 that aresupported on a base 192 having wheels 194. The uprights 190 arevertically slidable on the frame members 222 allow the vertical heightof the support table 216, and thus of the mandrel 74 to be adjusted.

In use, the mandrel 74 may be placed on the support table 216 of one ormore of the mobile carts 214, and the carts 214 may be rolled 224 intothe forming station 226, such that the mandrel 74 is aligned beneath theforming head 64. Alternatively, the mandrel 74 may be placed on thecarts 214 after the latter have been rolled 224 into the forming station226. In order to maintain alignment of forming head with the mandrel 74,a mechanical interlock 185 may be provided between the forming station226 and the mobile cart 214. After one or more prepreg plies have beenlaid up and formed in the forming station 226, the cart 214 may be usedto transport the fully formed stringer to another processing stationwhere the carts 214 may be used to handle or manipulate the stringer.For example, the carts 214 may be used to install the formed stringer ina cure tool (not shown).

Attention is now directed to FIGS. 37-40 which illustrate anotherembodiment of the former apparatus 244 which employs features of theembodiments previously discussed. The apparatus 244 comprises aplurality of individual former modules 174 mounted on a common base,which in illustrated embodiment, comprises a center support beam 262.The center beam 262 may be supported on one or more sets of wheels 260which provide the former apparatus 244 with mobility.

Each of the former modules 174 comprises a forming head 64 supported ona C-shaped frame 246. The C-shaped frame 246 includes an upright 248, alower arm 250 and an upper arm 252. A contoured mandrel 74 is removablymounted on the lower arms 250 (FIG. 37) by any suitable mechanism, suchas hand clamps 266. Each of the C-shaped frames 246 is mounted on thecenter beam 262 by a pair of vertical supports 264. The verticalsupports 264 are adjustably connected between the lower arm 250 and thecenter beam 262 by a series of brackets 268 and fasteners 269 receivedwithin ways 270 forming slides. The fasteners 269 (see FIG. 40)selectively fix the brackets 268 in any desired adjustment position.Adjustment of the position of brackets 268 in turn allows adjustment ofthe position of the C-shaped frame 246, and thus of the forming head 64,in both the Y-Z (roll) and X-Z (pitch) planes. Guide rails and linearactuators (not shown) may be employed for moving and adjusting thevertical supports 264 and the lower arm 250.

Each of the forming heads 64 may comprise a ply sweeper 65 attached toan assembly bar or frame 254 which is secured to the lower end of aguide rail 256. The individual ply sweepers 65 (tubes 96) are linkedtogether by the C-shaped frames 246 and the center support beam 262. Theadjustability of the C-shaped frames 246 provides the apparatus 244 withpassive compliance which allows adjustment of the sweepers 65 to matchlocal contouring of the mandrel 74. The guide rail 256 is mounted forlinear movement along the Z-axis on the outer end of the upper arm 252by two sets of guide rollers 258. A double acting pneumatic drivecylinder 182 mounted on the upper arm 252 has a piston rod 184 attachedto the forming head 64. The cylinder 182 displaces the forming head 64during the forming process, guided by the rail 256. In the illustratedembodiment, the ply sweeper 65 comprises a plurality of forming fingerson a tube 96, however, other embodiments of the ply sweeper 65previously discussed may be used.

Reference is now made to FIG. 41 which broadly illustrates the overallsteps of a method of forming a contoured composite prepreg laminate,such as the stringer 50 shown in FIGS. 1-5. Beginning at step 278, atleast one ply 82 of material such as a prepreg is placed on a contouredmandrel 74. Then, at step 280, the prepreg ply 82 is mechanically sweptover a first section of the contoured mandrel 74. Finally, at 282, theprepreg ply 82 is then vacuum formed over a second section, alsoreferred to as the flange sections 80 of the contoured mandrel 74.

FIG. 42 broadly illustrates the overall steps of a method of forming acomposite prepreg, hat-type stringer 50. Beginning at 284, at least oneprepreg ply is placed on a contoured mandrel 74. At 286, the prepreg ply82 is secured on a cap section 76 of the contoured mandrel 74. At step288, the prepreg ply 82 is swept over web sections 78 of the contouredmandrel 74. At 290, the prepreg ply 82 is held against the inside radii90 of the contoured mandrel 74. With the prepreg ply 82 held against theinside radii 90, then, at step 292, the prepreg ply 82 is then vacuumformed over flange sections 80 of the contoured mandrel 74.

Attention is now directed to FIG. 43 which illustrates a furtherembodiment of a method of laying up and forming highly contouredcomposite laminate stiffeners, such as a stringer 50. At 294, one ormore plies 82 are laid down on the mandrel 74 and swept over the capsection 76. Heat may be applied to the plies 82, as required, to softenthe plies 82 in preparation for forming, and/or to assist in tackingthem to the cap section 76. Next, at 296, the plies 82 are encapsulatedin a vacuum membrane, such as a flexible tube bag 105.

At 298, the mandrel 74 having the plies laid up thereon is transferredto and mounted in a former apparatus 244. At 300, each of the formingheads 64 of the apparatus 244 is aligned with the cap section 76 of themandrel 74. At step 302, a release film such as permeable Armalon® isinstalled over the encapsulated plies 82. In some embodiments, theArmalon® may be integrated into or removably attached to the formermodule 174, thus eliminating the need to perform step 302.

At 304, optionally, the forming fingers 102 are opened a distance thatis sufficient to clear the cap section 76. At 306 forming fingers 100are used to sweep the ply 82 over the web/flange radius of the mandrel74. At 308, the forming fingers 100 are used to hold the plies 82 at theinside radii 90 of the mandrel 74. At 310, vacuum is applied to the bag,resulting in the plies being vacuum formed down onto the flange sections80 of the mandrel 74. At step 312, the forming fingers 100 are retractedwhile vacuum is maintained against the plies 82.

The method described above in connection with FIG. 43 involves sweepingand then vacuum forming each ply 82. Other words, the plies 82 are fullyformed one-by-one onto all sections of the mandrel 74.

Alternatively, in another embodiment, multiple plies, or all of theplies may be swept over the web/flange radius before the flange sections80 are vacuum formed. Once the multiple plies have been formed over theweb/flange radius, then the entire group of plies is vacuum formed inorder to form the flange sections 80. In other words, the vacuum formingof the plies 82 down onto the flange sections 80 is performed only afterall of the plies 82 have been swept over the web/flange radius.

Attention is now directed to FIGS. 44-47 which illustrate an alternateembodiment of the forming head 64 comprising a ply sweeper 65 and apresser 316 mounted on a frame 254. The frame 254 is fixed on the lowerend of a guide rail 256 similar to the guide rail 256 forming part ofthe former module 174 previously described connection with FIGS. 37-39.The frame 254 and the guide rail 256 are vertically displaceable bypneumatic cylinder 182 (see FIG. 39). The cylinder 182 includes a pistonrod 184 that is attached to the guide rail 256 by a bracket 314. As willbe discussed below in more detail, the presser 316 is verticallydisplaceable independent of the vertical displacement of the ply sweeper65. In other words, the presser 316 may be displaced relative to the plysweeper 65. It should be noted here that while only a single forminghead 64 is illustrated in FIGS. 44-47, multiple forming heads 64 of thisembodiment can be employed in connection with the apparatus 195 shown inFIGS. 34-40 to form plies 82 on long mandrels 74. As will be discussedbelow, in an application where multiple forming heads 64 employed toform long stringer 50, the pressers 316 of the forming heads 64 areconnected together to form one continuous presser 316 having sufficientcompliance to conform to the contours of the mandrel 74 along itslength.

As best seen in FIGS. 46 and 47, in this embodiment, the ply sweeper 65comprises separate sets of curved, flexible forming fingers 100respectively secured to opposite sides of the frame 254. The formingfingers 100 terminate in fingertips 102 which are slightly spaced apartto form an opening 344 which extends along the length of the ply sweeper65. A pair of spaced apart, linear actuators 318 such as double actingpneumatic cylinders, or similar motor members, are mounted on the frame254 and each include a displaceable piston rod 320 that extendsdownwardly through the frame 254, between the opposing sets of fingers100, and passes through the opening 344 between the fingertips 102.

The lower ends of the piston rods 320 are connected to the presser 316by couplings 321. Each of the couplings 321 comprises a clevis 322provided with a clevis pin 324 that forms a pivotal connection 330between the ends of the piston rods 320 and a longitudinal rib 332forming part of the presser 316. The clevis pin 324 is slidable within aslotted hole 328 in the presser 316. The combination of the pivotalconnection 330 and the slotted hole 328 allow the presser 316 to bothlocally rotate (pivot) 329 and axially slide 326, thereby giving thepresser 316 the ability to conform to contours along the length ofcontoured mandrel (see FIG. 53) on which plies 82 are formed. Theability of the presser 316 to conform to the contours of the mandrel 74along its length allows a single presser 316 to be used to form plies 82on variety of mandrels 74 that respectively have different contours. Itshould be noted here that while two linear actuators 318 areillustrated, as few as one or more than two linear actuators 318 may beemployed to displace the presser 316 relative to the ply sweeper 65. Aswill be discussed later, the amount of force applied by the lineractuators 318 to the presser 316 may be varied during a formingoperation.

Referring now to FIGS. 46-50, the presser comprises a backbone-likecentral rib 332 to which the lower ends of the piston rods 320 arepivotally connected as previously described. The presser 316 furtherincludes flexible features in the form of a pair of outwardly extending,downwardly turned flexible wings 334. A foot 335 on the bottom of therib 332 extends between the two wings 334 and is shaped to match certainfeatures of the mandrel, which in the illustrated example, comprises theflat cap section 76 of a mandrel 74 that is configured to form ahat-shaped stringer having a flat cap. Where the stringer is to have acurved or domed cap, the foot 335 of the presser is cured to match thecurvature of the dome section of the stringer hat. The distance “D”between the outer extremities of the wings 334 is slightly greater thanthe width of the cap section 76, and the thickness “T” and height “H” ofthe rib 332 will depend upon application. The height “H” is dependent inpart on the selection of the material used to fabricate the presser 316as well as its required stiffness. The presser 316 is formed of amaterial such as a flexible plastic or rubber which has sufficientrigidity to transfer the necessary forming loads evenly along its lengthbetween support points without bridging due to local geometry changes ofthe mandrel 74. However, the presser 316 has sufficient flexibility toenable it to flex, deform and conform to the contours of the mandrel 74,avoiding any bridging over contours in the mandrel 74. While in theillustrated embodiment, the presser 316 is flexible to allow it to takethe shape of the contoured mandrel 74, in other examples, the presser316 can be substantially inflexible, i.e. rigid, and contoured to matchthe contour of the mandrel 74.

Referring now also to FIGS. 51 and 52, in applications where the presser316 is used to form a long composite part, such as a contoured stringerrequiring the use of multiple former modules 174 (see FIG. 37) andcorresponding forming heads 64, the presser 316 comprises a plurality ofpresser sections 316 a fastened together and arranged end-to-end to forma single, continuous presser 316 which is conformable along its lengthto the contours of the mandrel 74. The opposite ends of the pressersections 316 a are provided with laps 336 and fastener holes 341. Thepresser sections 316 a are assembled end-to-end such that the laps 336form half lap splice joints 342 between adjacent presser sections 316 a.The ends of the presser sections of 316 a are fixed to each other usingfasteners (not shown) passing through the fastener holes 341.

FIGS. 53-58 sequentially illustrate the movements and operation of theforming head 64 during a forming operation in which a contouredcomposite part, such as a stringer or other stiffener is formed toshape. Referring to FIG. 53, one or more plies 82 are placed over amandrel, which in the example, has a hat shape cross-section andincludes flange sections 80. The plies may be a woven or knitted cloththat are used to produce a fiber preform that is subsequently infusedwith a suitable resin prior to curing. In other examples, the plies 82may comprise a prepreg employing a material system that is suitable forthe application using one or more types of woven, knitted orunidirectional reinforcing fibers held in a thermoset or a thermoplasticresin matrix. After positioning the plies 82 over the mandrel 74, thecombination of the mandrel 74 and plies 82 are enclosed in a sealedvacuum bag 105 which is later evacuated during the forming operation.The forming head is vertically aligned above the centerline of themandrel 74, with the piston rod 320 fully extended to position thepresser 316 immediately beneath the fingertips 102 of the ply sweeper65.

Next, as shown in FIG. 54, the entire forming head 64 is displaceddownwardly, driven by the pneumatic cylinder 182 (FIG. 37) which formspart of a former module 174. As the presser 316 approaches the mandrel74 during this downward displacement, the wings 334 of the presser 316engage the cap section 76 and/or the web sections 78 of the mandrel 74,producing a lateral force that assists in centering the forming head 64relative to the centerline of the mandrel 74, while forming the ply overupper areas of the web sections of 78 of the mandrel 74. The passive,self-aligning function provided by the wings 334 may eliminate the needfor other mechanisms such as N/C driven devices, to precisely align theforming head 64 relative to the mandrel 74, resulting in greaterreliability and effectiveness of the forming fingers 100 in forming theplies 82 down onto the mandrel 74. As the presser 316 continues movingdown, the foot 335 of the presser 316 engages a portion of the ply 82and clamps it against the cap section 76 of the mandrel 74, therebypreventing the ply 82 from shifting laterally during the remainder ofthe forming process. The amount of clamping force applied to the ply inthis manner is controlled by the linear actuators 318. The amount offorce applied to the presser 316 by the linear actuators 318 can becontrolled during the forming sequence, unlike springs or other simplemechanisms used to load the presser 316. Consequently, for example,maximum force can be applied by the actuators 318 to the presser 316before the finger 100 commence the forming process, and thereafter, thepressure applied by the actuators 318 can be reduced as forming by thefingers 100 progresses.

As the forming head 64 continues to move down, the fingertips 102 of theply sweeper 65 engage and slide over the wings 334 of the presser 316(FIG. 56), and then form the ply 82 down over the web sections 78 of themandrel 74 (FIG. 57). The force applied by the pneumatic cylinder 182that moves the forming head 64 downwardly is greater than force appliedto the presser 316 by the linear actuators 318. Consequently, when thepresser 316 engages the cap section 76 of the mandrel 74 (FIG. 54), thepiston rod 320 begins retracting while linear actuators 318 continue toapply clamping force to the presser 316. FIG. 57 shows the fingertips102 of the ply sweeper 65 having fully formed the ply 82 down over theweb sections 78 of the mandrel 74. Then, similar to the embodimentspreviously described, the vacuum bag 105 is evacuated, causing the ply82 to be vacuum formed down onto the flange sections 80 of the mandrel74.

Attention is now directed to FIG. 59 which illustrates a system forforming contoured composite stiffeners using a plurality of formermodules 174 that incorporate the forming heads 64 previously describedin connection with FIGS. 44-58. Each of the former modules 174 includesa pneumatic cylinder 182 coupled through suitable directional flowcontrol devices 354, 356 and a pressure regulator 352 to a source ofpressurized and filtered air 358. As previously described, the pneumaticcylinders 182 control the displacement of forming heads 64, each ofwhich includes a pair of linear actuators 318, which in the illustratedexample, are also pneumatic cylinders 318 that control displacement ofthe pressers 316. While double acting pneumatic cylinders have beenillustrated, hydraulic cylinders or other power operated devices,including electric motors may be employed. Each of the pneumaticcylinders 318 are also coupled to the source of pressurized and filteredair 358 through a pressure regulator 360. The operation of the pneumaticcylinders 182, 318 is controlled by a controller 348 which may include amanually operated switch 349 that controls the up down displacement ofthe pneumatic cylinders 182, 318. In some applications, a line 350 maybe trained along the length of the apparatus spanning the former modules174 to allow an operator to operate the switch 349.

FIG. 60 broadly illustrates the overall steps of a method of forming acomposite stiffener contoured along its length. Beginning at 364, atleast one ply 82 of material is placed over a contoured mandrel 74. At366, a vacuum bag 105 is installed in sealed around the combination ofthe mandrel 74 and the ply 82. At 368, a forming head 64 is positionedabove and aligned with the mandrel 74, thereby aligning the ply sweeper65 and presser 316 with the mandrel 74. At 370, the presser 316 isextended relative to the ply sweeper 65 using a linear actuator 318. At372 a portion of the ply 82 is clamped against the mandrel 74 by movingboth the presser 316 and the ply sweeper 65 toward the mandrel 74,causing the presser 316 to force a portion of the ply 82 against themandrel 74. At 374 the ply 82 is swept down over the mandrel 74 whilethe portion of the ply 82 remains clamped against the mandrel 74. As theply sweeper 65 moves down over the mandrel 74, the cylinder rod of thepneumatic cylinders retract while maintaining a force on the presser316. At 376, remaining portions of the ply are vacuum formed onto themandrel 74 by evacuating the vacuum bag 105. Evacuation of the vacuumbag 105 also compacts the fully formed stiffener. At 378, the forminghead 64 is retracted, following which the composite stiffener is furtherprocessed (e.g. cured as by autoclave processing.

As previously mentioned, depending on the length of the compositelaminate stiffener being produced, it may be necessary to employ aplurality of the forming heads 64, in which case the presser sections316 a of the forming heads 64 are connected together (see FIGS. 51 and52). The connected presser sections 316 a essentially form onecontinuous presser 316 that is used to clamp the plies 82 against thecap section 76 of the mandrel 74 along its entire length, whileconforming to the longitudinal contours of the mandrel 74. The abovedescribed clamping action provided by the presser 314 prevents lateraldisplacement, and resultant misalignment of the plies 82 during thesubsequent sweeping action by the fingers 100 along the entire length ofthe plies 82. Thus, the method shown in FIG. 60 may also includeadditional steps, similar to those shown in FIG. 43, of assembling andaligning a plurality of the former modules 174 (FIG. 37) each having aforming head 64, interconnecting the presser sections 316 a of theforming heads 64 to form a continuous presser 316, aligning the formingheads 64, including the presser sections 316 a, above the mandrel 74,and clamping the plies 82 against the mandrel 74 along its contouredlength.

Embodiments of the disclosure may find use in a variety of potentialapplications, particularly in the transportation industry, including forexample, aerospace, marine, automotive applications and otherapplication where contoured elongate composite laminate stiffeners, suchas stringers, may be used. Thus, referring now to FIGS. 61 and 62,embodiments of the disclosure may be used in the context of an aircraftmanufacturing and service method 380 as shown in FIG. 61 and an aircraft382 as shown in FIG. 62. Aircraft applications of the disclosedembodiments may include, for example, without limitation, a variety ofcomposite structural members, including but not limited to stringers.During pre-production, exemplary method 380 may include specificationand design 384 of the aircraft 382 and material procurement 386. Duringproduction, component and subassembly manufacturing 388 and systemintegration 390 of the aircraft 382 takes place. Thereafter, theaircraft 382 may go through certification and delivery 392 in order tobe placed in service 394. While in service by a customer, the aircraft382 is scheduled for routine maintenance and service 396, which may alsoinclude modification, reconfiguration, refurbishment, and so on.

Each of the processes of method 380 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 62, the aircraft 382 produced by exemplary method 380may include an airframe 398 with a plurality of systems 400 and aninterior 402. Examples of high-level systems 400 include one or more ofa propulsion system 404, an electrical system 406, a hydraulic system408 and an environmental system 410. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the marine andautomotive industries.

Systems and methods embodied herein may be employed during any one ormore of the stages of the production and service method 380. Forexample, components or subassemblies corresponding to production process388 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 382 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 388 and 390, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 382. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft382 is in service, for example and without limitation, to maintenanceand service 396.

As used herein, the phrase “at least one of”, when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used and only one of each item in the list may be needed. Forexample, “at least one of item A, item B, and item C” may include,without limitation, item A, item A and item B, or item B. This examplealso may include item A, item B, and item C or item B and item C. Theitem may be a particular object, thing, or a category. In other words,“at least one of” means any combination items and number of items may beused from the list but not all of the items in the list are required.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different advantages as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. Apparatus for forming plies of material onto a mandrel having contours, comprising: a ply sweeper for sweeping the plies onto the contours of the mandrel; a presser independently displaceable relative to the ply sweeper for pressing a portion of the plies against the mandrel; and at least one powered actuator coupled with the presser for displacing the presser relative to the ply sweeper.
 2. The apparatus of claim 1, wherein the ply sweeper includes a tube having a plurality of slots therein and fingers defined between the slots configured to engage and press the plies against the contours of the mandrel.
 3. The apparatus of claim 1, wherein: the powered actuator includes a pneumatic cylinder having a cylinder rod, and a coupling connecting an end of the cylinder rod with the presser.
 4. The apparatus of claim 3, wherein the coupling includes a slot in the presser and a pivotal connection slidable within the slot.
 5. The apparatus of claim 1, wherein: the presser includes a plurality of presser sections attached to each other and arranged end-to-end, and each of the presser sections is formed of a flexible material allowing the presser to conform to the contours of the mandrel.
 6. The apparatus of claim 1, wherein the presser includes: a rib connected to the powered actuator, and a pair of flexible wings extending outwardly from the rib and engageable with the mandrel.
 7. Apparatus for forming composite plies on a mandrel contoured along its length and having a cap, a pair of webs and a pair of flanges configured to form a hat-shaped stringer, comprising: a frame; a ply sweeper mounted on the frame and configured to sweep the composite plies down onto and over the pair of webs of the mandrel; a presser mounted on the frame and extendable relative to the ply sweeper, the presser being configured to press a portion of the composite plies against the cap of the mandrel; and at least one linear actuator mounted on the frame and coupled with the presser for extending the presser relative to the ply sweeper.
 8. The apparatus of claim 7, wherein: the ply sweeper includes a tube having a plurality of slots therein and fingers defined between the slots configured to engage and press the composite plies against the webs of the mandrel.
 9. The apparatus of claim 7, wherein the linear actuator is a pneumatic cylinder mounted on the frame and having a displaceable piston rod coupled with the presser.
 10. The apparatus of claim 7, wherein: the ply sweeper includes opposing sets of spaced apart, flexible fingers having fingertips, and the presser is extendable by the linear actuator beneath the fingertips.
 11. The apparatus of claim 7, wherein: the presser includes a plurality of presser sections attached together and arranged end-to-end, and the presser is formed of a flexible material allowing the presser to conform to the contoured length of the mandrel.
 12. The apparatus of claim 7, further comprising: a coupling between the linear actuator and the presser allowing the presser to conform to the contour of the mandrel.
 13. The apparatus of claim 12, wherein the coupling includes a slot in the presser and a pivotal connection slidable within the slot connecting the presser with the linear actuator.
 14. The apparatus of claim 7, wherein the presser includes a rib connected to the linear actuator and a pair of flexible wings extending outwardly from the rib and engageable with the pair of webs of the mandrel.
 15. A method of forming a composite stiffener contoured along its length, comprising: placing at least one composite ply over a mandrel; positioning a ply sweeper and a presser above the mandrel; extending the presser relative to the ply sweeper using a linear actuator; clamping a portion of the composite ply against the mandrel, including moving the presser and the ply sweeper toward the mandrel until the presser forces the portion of the composite ply against the mandrel; and sweeping the composite ply down over the mandrel while the portion of the composite ply is clamped against the mandrel.
 16. The method of claim 15, wherein extending the presser includes extending a pair of piston rods.
 17. The method of claim 16, further comprising: retracting the pair of piston rods as the ply sweeper sweeps the composite ply down over the mandrel.
 18. The method of claim 15, further comprising: attaching a plurality of presser sections together end-to-end; and pivotally coupling the presser with the linear actuator to allow the presser to conform to the contoured length of the mandrel.
 19. The method of claim 15, wherein clamping a portion of the composite ply against the mandrel includes applying a force to the presser using the linear actuator.
 20. The method of claim 15, wherein clamping a portion of the composite ply against the mandrel includes centering the presser on the mandrel using flexible features on the presser. 